[Intel-gfx] Flicker-free boot in DRM

[Adam Jackson]

On 10/30/11 12:24 AM, Keith Packard wrote:
> On Sat, 29 Oct 2011 00:05:22 -0700, "Keith Packard"<keithp at keithp.com>  wrote:
>
>>   *  I've got LVDS pulling the current mode out of the hardware
>
> With a machine that has a native VBE mode for the panel, the problem is
> that clock computed from the hardware settings is not quite the same as
> the clock requested in the mode. I think the clock computation must be
> slightly off, but even with that fixed, it will probably not quite
> match. I think we'll need a magic flag in this mode telling DRM to allow
> a bit of fuzz in clock matching.

Yeah, it won't be precise.  That's why there's PLL search code at all, 
and why it has a fuzz factor for finding "good enough".

I ran the math for the maximum error in the PLL search back when I was 
fixing a case where it fell through and failed to find timings at all. 
See 6ba770dc5c334aff1c055c8728d34656e0f091e2.

- ajax